Process for reducing the viscosity characteristics of nitrocellulose



Patented Feb. 9, 1926.

A UNITED STATES LEONARD E. BRANCHEN, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK PATENT OFFICE.

COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

PROCESS FOR REDUCING THE VISCOSITY CHARACTERISTICS OF NITROCELLULOSE.

No Drawing.

7 To all whom it may concern:

Be it known that I, LEONARD E. BRANoHnN, a citizen of the United States of America, residing at Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Processes for Reducing. the Viscosity Characteristics of Nitrocellulose, of which the following is a full, clear, and exact specification.

This invention relates to processes for reducing the viscosity characteristics of nitrocellulose. One object of the invention is to provide a safe, simple andinexpensive process for reducing said viscosity characteristics within a comparatively short time. Another object of theinvention is to provide a procass for reducing rapidly and accurately the viscosity characteristics of the nitrocellulose when it is in the solid colloidized state and even when mixed with high-boiling organic compounds. Another ob ect 1s to provide a process which is successful at atmospheric pressure and room temperature. Another objectv of the invention is to providea proc ess in which the nitrocellulose remains subare nearly always, of the high-viscosity species. It is, therefore, desirable to provide a suitable process for lowering the viscosity characteristics of nitrocellulose, particularly when the latter is in solid colloidized form,

. and associated with high-boiling compounds,

like camphor and butyl alcohol, in inexpensive or waste materials.

I have found that such a process can be carried out by first softening the nitrocellulosic material with a suitable liquid and thereafter treating it with an aqueous alkaline solution. The softening step, which'is carried out preferabl by a penetrant liquid, makes the nitroeel ulosic material more Application filed my 13, 1925. Serial No. 30,082. i

. readily susceptible to the action of'the alkaline solution and thereby shortens thenecessary time for producing the desired result. Various penetrant liquids may be employed such, for example, as one which softens the nitrocellulosic material, like films and has a solvent action on high-boiling organic compounds therein like camphor, butyl alcohol, triphenyl phosphate, monochlornaphthalene, and thelike. It is sometimes useful to control the action of an especially strong penetrant by diluting it with water; and in any event the softening action is stopped before the nitrocellulose itself is substantially dissolved. l

The treatment with an aqueous alkaline solution may be carried out in many different ways; but the simplest is to operate at room temperature and, atmospheric pressure; Moreover, -it is advantageous to use dilute solutions so that the nitrocellulose will not be deteriorated by saponification. I prefer to employ an aqueous solution of an alkali'that supplies less hydroxyl ions than a 5% aqueous solution of sodium hydroxid. In fact, a much weaker solution than that can be employed, such, for example, as one equivalent to a 2% solution of carbonate of soda. When working with dilute solutions the action can be expedited by heating the 'bath, but this is not necessary for practical results, since the desired effect can usually be obtained at room temperature in about 3 days. The most useful alkalies to use are the carbonates or hydroxide of the alkali metals, by which term I include the ammonium compounds,.as well as those of sodium, potassium, lithium, etc.

I have also found that it is a great advantags to have a bleaching agent present in the alkaline bath. nitrocellulose, so asto yield a superior product, but may assist the. alkali in bringing about a reduction in the viscosity characteristics. agents may be employed,.I find it sufficient to bubble chlorine gas into the bath, the amount depending upon the needs for bleaching. A 7

I shall now describe one embodiment of my invention, but it will be understood that the latter is not restricted to the illustrative details except as indicated in the appended claims. The material to' be treated is preferably comininuted. Solid colloidized nitrolVhile any of the usual bleaching It not. only decolorizes the cellulose, such as pyroxylin waste, or film chopped up to a suitable size.

scrap from which the gelatinous coatings have been removed in the usual way, is

The co-mminuted material is then treated by the penetrant liquid, say a bath of methyl alcohol toned down by 5% of water. The

r m terial is allowed to soften in contact with this liquid, preferably. by being immersed in it, for 1 tot hours at room temperature and atmospheric pressure. In any event thebonate in wat-enwith the desired amount of cessi've baths ofwater.

chlorine gas bubbled in to produce a. colorless product, is excellent. The viscoslty characteristics of the nitrocellulose are usually reduced in such a bath to the desired point in about 3 days at room temperature and atmospheric pressure. The duration of the action can be readily found by test, say by removing representative samples, dissolving them and making the customary viscosity determinations.

When the end point is reached, the bath is drained from the material and the latter is washed in any suitable way, say by treating it for several days in running water, or by giving it a plurality ofsoaklngs 1n suc- Purification may be hastened by using baths of hot water, say at 7 5 G. I Instead of the mixture of water and methyl alcohol described above, I may employ ordinary denatured ethyl alcohol, of. the kind containing a small-amount of methyl alcohol. This operates onaverage nitro- -cellulosic materials in about 24 hours at room temperature and atmospheric pressure. a

The product obtained by the abovev de scribed process has been found to beespecially free from color and from harmful acidity, as well as remarkably stable.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is: i

1. The process of treating nitrocellulose, which comprises first softening it wlth a penetrant liquid, and thereafter acting on it separately with an aqueous solution of an alkali until the viscosity characteristics of the nitrocellulose. are reduced.

2. The process of treating solid colloidized nitrocellulose associatedywith a high-boiling or anic compound, which comprises first softening it with a penetrant liquid, which has a solvent action on said organic/compound, "and thereafter act ng on said material with an aqueous solution of an alkali until the viscosity characteristics of the nitrocellulose are reduced.

" 3. The process of treating solid colloid ized nitrocellulosic material, which comprises softening it with a penetrant liquid containing water and anactive nitrocellulose solvent, stopping the. action of said liquid before the nitrocellulose is dissolved, and thereafter acting on it with an aqueous solution of an alkali until the viscosity characteristics of the nitrocellulose are reduced.

4. The process of treating solid colloid- .ized nitrocellulose associated with'a highboiling organic compound, which comprises softening'it with a mixture of water and methyl alcohol, and stopping the action before the nitrocellulose is dissolved, and thereafter acting on it with anaqueous solution of an alkali until the viscosity characteristics of the nitrocellulose are reduced.

5. The process of treating solid colloidized nitrocellulose, which comprises acting thereon with a' penetr'ant liquid, from 1 to 24 hours at room temperature the action being stopped beforethe nitrocellulose is dissolved, and thereafter acting on it separately with an-a'queous solution of an alkali until the viscosity characteristics of the nitrocellulose are reduced. v

6. The process of treating solid-colloidized' nitrocellulose, which comprises softening it with a penetrant liquid, and thereafter acting on it separately with an aqueous solution of an alkali that supplies less hyboiling organic compound, which comprisessoftening it with a penetrant liquid which has a solvent action on said organic compound, and thereafter acting on'it'with an aqueous solution of an alkali that supplies less hydroxylions than a 5% solution of sodium hydroxid, until the viscosity characteristics of the nitrocelluloseare reduced. 8. The processfof treating solid colloidized nitrocellulose, which comprises softening it with apenetrant liquid, and there after acting on 11: separately with a 2% solution of a carbonate of an alkali metal, until the viscosity characteristics of the nitrocellulose are reduced.

9. The process of treating nitrocellulose, which comprises softenin it with a penetrant liquid, and thereafter acting on it separately with an aqueous solution of an alkali and a bleaching agent, until the viscosity characteristics of the nitrocellulose are reduced.

10. The process of treating solid colloidsoftening it with a penetrant liquid which.

ized nitrocellulose associated with a high boiling organic'compound, which Comprises has a solvent action on said organic compound, and thereafter acting on 1t Wlth an aqueous solution of an alkali that supplies less hydroxylfions than 215% solution of sodium hydroxid, said solution containing a bleaching agent, and said action bei ngcontinueduntil the viscosity characteristics of the nitrocellulose are reduced. 11. The process of treating comminut'd film scrap which comprises softening it with i a bath of Water and methyl alcohol for 1 to 5 hoursat room temperature, the softening being stopped before the nitrocellulose. is dissolved, and thereafter acting on said film scrap With a 2% solution'of sodium carbonate containing chlorine for 1 to 3 days at room temperature.

Signed at Rochester, New York, this 22nd day of April 1925.

LEONARD E. BRANCHEi 

